We now specify only CSST with higher rated insulated jacketing, such as the new enhanced product from Omegaflex (the new '2nd gen' CounterStrike)

One useful presentation was made available here: http://www.lightning.org/sites/www.lightning.org/files/documents/09_Presentation-Morgan-CSSTs.pdf

We have considered adding a requirement for field application of insulating wrap/tape within 6 inches of connection to appliance, though the liability of 'who takes credit/blame' for any field installed addition of insulating material is...uncomfortable... Has anyone here seen or added any such requirement to attempt to reduce the chances of an arc from the service-bonded appliance/cabinet to the nearby incoming portion of the outside-GEC-bonded CSST?

OK. Enough is enough, The charge is not jumping from the CSST to the metal duct the charge is jumping from the non-grounded steel duct to the CSST. There is no equipontial between these two systems when the high induced transients are in play. Ground and bond the duct so that both systems rise and fall equally and have a pathway to the grounding electrode.

While bonding CSST at its ends may help, I wonder if there are any data about the ability of the thin corrugated steel's ability to safely carry currents from a lightening strike? I note Chas Bruner's comment about the potential for discharge at bends in tubing runs and suspect that the product's selling point - ease of installation - may also be its safety weakness. Another point is that these installations are often not coordinated with an electrician, making the installing plumber responsible for proper bonding. I've noticed many CSST retrofit installations in existing homes - none have been bonded.

As I understand it, arcing on CSST can occur where it is bent because the static charge will jump the gap to the nearby surface of the CSST rather than follow the surface of the corrugation because that is the path of least resistance. This can cause a perforation and an ignition source and dosen't need to be close to another grounded surface to cause the problem.

As an electrical inspector I struggle with this issue daily. The National Electrical Code specifically prohibits the use of metal underground gas piping as an electrode. (per 250.52-B-1) In central Minnesota copper gas piping is commonly buried from the home to the propane tank. The manufacturer of the CSST has contacted the gas company in my area and informed them not to hook up gas unless the gas piping system has been bonded. I feel that the CSST manufacturers are overlooking every other code to protect themselves from liability. I belive the CPSC should get involved and require additional product testing. As a relatively new product I belive we've only seen the tip of the iceberg as far as fires caused from this product.

What is the proper bonding methods to be used with CSST ?

Thanks for the report as many do not see these reports from isolated news sources, I have been warning GC's and home owners including plumbers about this problem for a few years now, and I can not see a safe way to guard it from a direct lightning strike,

The problem starts with what this product is being connected too, most appliances that are connected to it will have flues and or chimney's that penetrate the roof line and in many cases can be the highest point above a roof, this is like you are just asking for lightning to strike it, second the understanding of how lightning current propagates through a conductive path is very little understood by many who are evaluating on how to protect this product, lightning has a high frequency component that just like in radio frequencies can follow paths that make no sense to the basic laymen who only understand DC or low frequency AC such as the power supply to our houses, simply bonding one end of the gas supply system is not enough, as the lightning current can and will flow do to the high frequency impedance of this bonding path, what I can't believe is that I can't find any info on where someone who knows more about lightning who that would be more qualified to develop a protection method for this product has been doing any testing, if there has been it has not been made very public, and this is the University Of Florida, with their knowledge from test preformed at camp Blanding, this would have been where they should have gone a long time ago. One of the reasons I feel this hasn't been done is that with my knowledge of lightning I think the proper protection of CSST with the added extra cost of the product would render it not a very good cost alternative to other known safer methods of gas piping, I would expect that not only would providing a protection system of the flues or chimneys that rise above the roof line have to be done, but parallel bonding at the appliance back to the electrode system would also have to be done to lower the impedance path for the lightning energy back to the GES to limit the amount of energy of the lightning placed on the product.

Just yesterday, lightning struck a home in my small town, the gas flex line to the heater ruptured, and the resulting fire did a lot of damage.

Although primarily a design professional, i also do a significant number of fire investigations each year. Several years ago we began seeing residential fires caused by small leaks in the flexible gas lines where they entered the furnace. After the third incident in one year I decided to check my own furnance - and there it was, a hole in the tubing at the point closest to the sheet metal. So this, regardless of the cause, this is no myth!

It is our belief that there are two possible causes for these holes. First, they may be a result of friction, second, they may be caused by arcing between gas piping and the furnace sheet metal during a lightning storm. If the two are are not well bonded sufficient potential difference can develop between the two and cause an arc. In any case, most, if not all the cases which we investigated, were associated with lightning storms.

The moral is, don't use flex except where absolutely necessary. It MUST NOT be used to pass through an opening in the sheet metal of a furnace or other equipment - use a piping nipple where the line passes in. And whereever flex is used, ensure it is properly bonded to any grounded metal close by.